As the sustainability of traditional energy sources and storage methods has come into question, recent research has focused on the development of novel energy conversion and storage devices. Presently, conventional lithium-ion batteries are widely used in part because of their high gravimetric energy densities (˜200 Wh/kgcell at ˜1 kW/kgcell). However, lithium-ion batteries can achieve high-power performance (>50 kW/kgcell) only at the expense of cell robustness and safety. Next-generation energy storage applications, such as load-leveling and electrified propulsion, require higher levels of energy and power performance. Accordingly, there remains a need for energy storage devices that provide both high energy density and high power capability.
Future applications for electrochemical energy storage will demand both high gravimetric energy and power. To meet these goals, there is a need for devices that can span the performance gaps between existing technologies, which include lithium-ion batteries and electrochemical capacitors (ECs or supercapacitors). Energy storage devices desirably have a variety of additional properties, such as long cycle life, compact size, light weight, operational safety, and flexibility. The nature and properties of electrodes in an energy storage device determines the overall performance of the device.